1. Field of the Invention
This invention relates to an electrically operated pressing tool for connecting tubular workpieces, with a fork-like receiver, with a clamping pincer exchangeably held in the receiver by a connection bolt, and with a controlled electric drive motor for actuating the clamping pincer, wherein there is a spindle driven by an electric drive motor via a reduction gear and which is in active connection with the clamping pincer.
2. Discussion of Related Art
Portable, electrically functioning pressing tools are used for pressing coupling elements such as press sleeves, press fittings, connecting sleeves, tube sections inserted into one another and likewise. The pressing tools have a clamping pincer with clamping jaws which form a pressing space for receiving the coupling element to be pressed. A pressing pressure required for the pressing is initially produced by an electric motor connected to the mains, via a forward and rearward running spindle which acts on a yoke having two rollers, wherein the rollers move the clamping jaws of the clamping pincer.
These pressing tools are proven and are extremely widespread. Through development pressing tools have moved more and more from spindle-operated versions to hydraulically operated versions. With these hydraulically functioning tools one operates with an electromotoric drive which actuates a pump that displaces a piston having a piston rod that acts on the yoke in which the two rollers are mounted. These hydraulically operated pressing tools may be controlled precisely by a combined monitoring of the hydraulic pressure to be built up as well as the monitoring of the path which checks an exact closure of the clamping pincer.
A further advantage of hydraulically functioning pressing tools is that battery-operated electric motors may also be applied, by which one may operate independently of the mains. With the hydraulic drive one may also apply battery-operated electric motors which initially have a relatively low torque.
For all previously mentioned pressing tools, one applied different clamping pincers corresponding to a large number of different coupling elements for a large range of the most varied of diameters. The diameters of common coupling elements are in the range of 10 to more than 100 mm. The most common range of application however is between 10 and 30 mm. However, practically all pressing tools offered on the market today are designed for the complete application range. Accordingly, the pressing tools known today are relatively large and heavy. Although there exists a corresponding demand for portable, smaller and lighter pressing tools for the most common range between, for example 10 and 50 mm diameter of the coupling elements, such apparatus are not obtainable on the market until today because the safety issues and monitoring of the pressure which is built up by the pressing tools. The high pressures built up with hydraulic systems require a correspondingly heavy and safe design of the pressing tool and a corresponding reduction which with respect to scale is not possible without using completely different clamping pincers. In order to obtain the required safety with spindle-operated pressing tools, between the electric motor and the spindle there is arranged a clutch in front of or after the gear, for safety reasons. This has made the spindle-operated apparatus heavier, more expensive and larger. Various suppliers have brought this type of apparatus to the market.
From U.S. Pat. No. 6,035,775 there is known a pressing tool functioning with a spindle, with which the built up pressure is electronically monitored because the rotation speed of the electric motor is monitored and is controlled with a predefined profile within a certain bandwidth. These pressing characteristics are essentially dependent on the size, shape and nature of the material of the coupling elements and thus permit a pressing procedure which is carried out in a pressure-dependent and time-dependent manner.